/*
*    Qizx/open 3.0 beta
*
* This code is the open-source version of Qizx.
* Copyright (C) 2004-2009 Axyana Software -- All rights reserved.
*
* The contents of this file are subject to the Mozilla Public License 
*  Version 1.1 (the "License"); you may not use this file except in 
*  compliance with the License. You may obtain a copy of the License at
*  http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
*  WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
*  for the specific language governing rights and limitations under the
*  License.
*
* The Initial Developer of the Original Code is Xavier Franc - Axyana Software.
*
*/
using System;
using EvaluationException = System.Qizx.Api.EvaluationException;
using System.Qizx.XQuery;
using EmptyException = System.Qizx.XQuery.Impl.EmptyException;
using ErrorValue = System.Qizx.XQuery.Impl.ErrorValue;
namespace System.Qizx.XQuery.Op
{
	
	public class InstanceofExpr:BooleanExpression
	{
		private Expression expr;
		
		private XQType testedType; // hides member of super class
		
		public InstanceofExpr(Expression expr, XQType testedType)
		{
			this.expr = expr;
			this.testedType = testedType;
		}
		
		public override Expression Child(int rank)
		{
			return (rank == 0)?expr:null;
		}
		
		public override Expression StaticCheck(ModuleContext context, int flags)
		{
			expr = context.staticCheck(expr, 0);
			type = XQType.BOOLEAN;
			return this;
		}
		
		public override void  Dump(ExprDisplay d)
		{
			d.header(this);
			d.child("expr", expr);
			d.property("testedType", testedType);
		}
		
		public override bool evalAsBoolean(Focus focus, EvalContext context)
		{
			try
			{
				XQValue v = expr.eval(focus, context);
				v = v.CheckTypeExpand(testedType, context, false, false);
				if (v is ErrorValue)
					return false;
				return true;
			}
			catch (EmptyException e)
			{
				// the trick
				return testedType.isOptional();
			}
		}
	}
}